revert arm64 change
revert arm64 change

This commit removes the arm64 change because it caused issues
with Go 1.4.

Fixes #416.

brahmaroutu/bolt,mashuai/bolt,yew011/bolt,benbjohnson/bolt,tv42/bolt,chlorm-forks/bolt,etcd-io/bbolt,joyrexus/bolt,mr-justin/bolt,btcsuite/bolt,raggi/bolt,li-ang/bolt,nilslice/bolt,boltdb/bolt,tvmaly/bolt,hvnsweeting/bolt,dindinet/bolt-1,wyzssw/bolt,Compasses/bolt,samanalysis/bolt,pombredanne/bolt-2